Throughout industrialized countries, electrical power transformers are placed at spaced intervals as intergral parts of an electrical power distribution system to bring electrical service to high density dwelling areas. These electrical power transformers step down the high voltage electrical current that is used for efficient long distance electrical power transmission to voltages of 110, 115, 220, 440 and other voltages commonly used to provide alternating current services to home and industrial subscribers by electrical utility companies.
The electrical transformers which are predominately employed to provide this home and industrial service usually weigh between about 300 and about 2,000 pounds.
Because the electrical transformers employed are installed for permanent operation, they must be supported upon a platform or mounting above the level of the ground soil, shrubbery, and ground water which might impair their operation. The transformers must be installed in positions to resist deterioration and degradation from environmental elements.
Several types of transformer mountings are currently used. Before the introduction of transformer mounting pads manufactured from plastic, pads were either cast in place or pre-cast using concrete. Although they are easier to manufacture, plastic pads have failed to adequately support transformers because of the effects resulting from heat generated by the transformers combined with ambient heat from the environment. The combined thermal effect causes the plastic transformer pads to soften with the result that the transformers sink into the plastic surface of the mounting pads. This poses problems of servicing transformers. Specifically, with typical transformer design, once the transformer sinks into the skin of the pad, the service panel is trapped and cannot be opened.
Another problem in conventional plastic transformer pads occurs because of the constant vibration of the working transformer. The instability of conventional plastic pads results in the transformer being tilted, thereby affecting the efficient operation of the transformer.
All of the alternative types of transformer pads or mountings involve significant disadvantages. In the case of concrete pads, the mounting may either be obtained in pre-cast form or poured in place at the job site. Mountings which are poured in place are usually expensive since the necessary forms, aggregate, equipment, etc. must be brought to the job site. In addition, this on-site construction of concrete mountings pads is extremely labor intensive and therefore quite expensive.
Another conventional type of mounting pad which is sometimes employed is a pre-cast concrete mounting structure. Such a structure is not as expensive to manufacture, since it is produced at a manufacturing site. However, pre-cast mounting supports weigh from 600 to 800 pounds and are quite difficult to transport and handle. Moreover, the pre-cast concrete mounting structures are frequently broken or cracked as they are manipulated into position.
Another alternative type of transformer-mounting pad which is currently employed is that formed entirely of fiberglass. Such a fiberglass structure is held together by a thermosetting plastic which may include an epoxy or polyester resin. Although functional and weather resistant, the fiberglass structures are expensive, as the cost of the materials used in their construction is quite large.
As previously noted, there have been attempts to produce a satisfactory transformer mounting from plastic. Such mounting supports are formed from a quantity of plastic, typically polyvinylchloride or polyethylene, which is poured into an enclosed mold. The mold is rapidly rotated so that centrifugal force causes the plastic to cover the interior walls of the mold. When cured, the hollow plastic structure may be removed and filled with a core of a supporting material, such as polyurethane foam. Alternatively, the rotationally cast structure may include aluminum reinforcing strips which are positioned within the mold prior to rotational casting. The finished product then includes the aluminum reinforcing strips entrapped within the structure employed as a transformer mounting.
As has been explained, however, such rotationally cast mounting pads tend to deteriorate due to their thermal and mechanical instability.